The present invention relates to a device for applying compressive pressures against a patient's limb through means of a compression sleeve enclosing the limb, and, more particularly, to a circuit for preventing the application of excessive pressure and to control the application of pressure to a ventilation chamber of the sleeve.
Compression sleeves and devices for controlling them are well known and illustrated in the patent art such as U.S. Pat. Nos. 4,013,069 of Hasty; 4,030,488 of Hasty; 4,091,804 of Hasty; 4,029,087 of Dye et al; 3,942,518 of Tenteris et al; and 2,145,932 of Israel, and reference may be had thereto for general background information of structure and utility.
Briefly, a flexible compressive sleeve having a plurality of pressure compartments is wrapped around the limb of a patient, and the compartments are then intermittently pressurized to successively apply pressure compression to different parts of the limb.
One potential problem with such devices is that due to malfunction, the pressure can become so great as to discomfort or even injure the patient. Accordingly, in known devices such as those shown in the above patents, pressure release valves have been provided to prevent such occurrence. The release valves, however, tend to be relatively slow acting and do not function to terminate power to the compressor or other pressure source.
In U.S. Pat. No. 4,091,804, a sleeve is disclosed which is provided with a ventilation chamber having openings which face inwardly toward the patient's limb to inject air between the limb and the sleeve to ventilate or cool the limb. A need therefore exists for means to control the application of pressure to the ventilation chamber in coordination with the application of power to the pressure chamber.
Known controllers have been constructed from fluidic or pneumatic controls. While such types of controls function in an acceptable manner, they are subject to mechanical wear and other deterioration.